The smog may pose a risk to people gathering in town and city centres where busy roads will be chock-full cars carrying families as they hit the shops.

Dr Penny Woods, chief executive of the British Lung Foundation, said: “During periods of moderate or high pollution, people with respiratory conditions, such as COPD and asthma, can find their conditions worsening.

“To minimise this impact, people should avoid pollution hotspots, such as busy roads, particularly during rush hour.